In reply to Billhook:
> Wow? 2 ltr. I've never carried that much water on the hill ever.
Apart from the fact that folk are doing different activities in various conditions and water consumption is very down to an individual, a larger bladder does not take much more space/weight compared to a hard bottle. E.g. Camelbak Crux 2L bladder weighs 210g and 3L one weighs 235g.
It's nice to have some spare space for water when camping or bothying. Refilling 2 litres of water before I take boots off means I can cook dinner and have enough water for breakfast/coffee. Then I can refill as much as I need before I leave the site.
I usually take 1 litre Nalgene bottle in winter and swap it to a 2 litre Source hydration bladder (with a wide opening) for warmer months.